FIG. 1 shows a common configuration of alkaline batteries. The illustrated alkaline battery is an LR14 alkaline battery 1 having a cylindrical shape; FIG. 1(A) is a longitudinal sectional view in which the direction of the cylinder axis 10 is a longitudinal direction, and FIG. 1(B) is a magnified view of a circle 100 in FIG. 1(A). The alkaline battery 1 has a so-called inside-out construction. The alkaline battery 1 includes: a cylindrical cell can (cathode can) 2 which is made of metal and has a bottom; a cathode mixture 3 which is annular in shape; a cylindrical separator 4 which is disposed inside the cathode mixture 3 and has a bottom; an anode gel 5 which contains zinc alloy and fills the separator 4; an anode electron collector 6 inserted into the anode gel 5; a negative plate 7; a sealing gasket 8; and the like. In this configuration, the cathode mixture 3, the separator 4, and the anode gel 5 serve as active parts of the alkaline battery 1 in the presence of an electrolytic solution. The inner surface of the cathode can 2 is exposed to a strong alkaline electrolytic solution. Therefore, as shown in the magnified view of FIG. 1(B), a substrate of the cathode can 2 is a steel sheet 21 on which a nickel-plated layer 22 of approximately 0.6-1.0 μm thickness is formed. Thus, the nickel-plated layer 22 on at least the inner surface side of the cathode can 2 prevents iron that constitutes the steel sheet 21 from being corroded by the strong alkaline electrolytic solution.
The cathode can 2 which also serves as a cell case has a positive terminal 9 on the bottom face thereof. The inner surface of the cathode can 2 is in direct contact with the cathode mixture 3, which enables the cathode can 2 to function as a cathode current collector. Therefore, it is necessary to lower as much as possible a contact resistance between the cathode can 2 and the cathode mixture 3. In order to lower further the contact resistance, an electro-conductive film 23 to which an electro-conductive paint is applied is generally formed on the inner surface of the cathode can 2.
The following [PTL 1] describes a technique which for maintaining low contact resistance for a long time by forming on the inner surface side of a cathode can a coating which contains elemental Co or cobalt compound.